[cfe-dev] [RFC] New ClangDebuggerSupport Library

[Chris Bieneman via cfe-dev]

> On Nov 11, 2016, at 9:20 AM, David Blaikie via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> 
> 
> 
> On Fri, Nov 11, 2016 at 9:08 AM Reid Kleckner <rnk at google.com <mailto:rnk at google.com>> wrote:
> On Fri, Nov 11, 2016 at 8:13 AM, David Blaikie via cfe-dev <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote:
> My knee-jerk reaction is that this could just as well live in LLDB if there are no other users - though Keno points out he could use it in Julia, so that seems like potentially sufficient interest to demonstrate that it might be a reasonable/reusable abstraction.
> 
> I think this functionality should live in the clang codebase. The AST has a surprising number of invariants that are easy to violate. Right now LLDB is super tightly coupled to clang because it has to carefully learn and satisfy those invariants.
> 
> I'm not sure having it in the Clang codebase is going to make that much/any easier to satisfy, it may shift the burden to the Clang project/developers which is why I wonder whether it's a cost worth adding to the Clang project/gating Clang changes on. If it's a service Clang (as a project) thinks is worth vending to users, sure enough.

I think that shifting the burden of keeping it working to Clang is good for anyone who wants LLDB to be a stable and reliable debugger, which I think is good for (the Royal) LLVM.

>  
> The approach taken in LLDB is to essentially "deserialize" DWARF into ASTs. If we consider DWARF to be a stable serialization of the AST,
> 
> I wouldn't really think of it that way - for one thing, there's lots of DWARF generated by things other than Clang (even for C++), so I don't see the symmetry quite as much here.

I agree with Dave here. We can’t really think of DWARF as a bi-directional serialization to ASTs. We really need to be able to generate reasonable ASTs from DWARF created by multiple versions of Clang, GCC, ICC, and any other C/C++/Obj-C(/Julia) compiler anyone wants LLDB to support. 

-Chris

>  
> then the reading logic should live near the writing logic, which is currently in clang/lib/CodeGen/CGDebugInfo.cpp.
> 
> Just my 2c.
> 
> - Dave 
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